1,4,5,8-Tetrahydro-1,4;5,8-diepoxyanthracene reacts with various anthracene endcapped polyimide oligomers to form Diels-Alder cycloaddition copolymers. The polymers are soluble in common organic solvents, and have molecular weights of approximately 21,000 to 32,000. Interestingly, these resins appear to be more stable in air then in nitrogen. This is shown to be due to a unique dehydration (loss of water ranges from 2 to 5 percent) at temperatures of 390 to 400 C to give thermo-oxidatively stable pentiptycene units along the polymer backbone. Because of their high softening points and good thermo-oxidative stability, the polymers have potential as processible, matrix resins for high temperature composite applications.